Improving Decision Speed, Accuracy and Group Cohesion through Early Information Gathering in House-Hunting Ants

Nathalie Stroeymeyt,Nigel R Franks,Martin Giurfa,Brock Fenton

doi:10.1371/journal.pone.0013059

Abstract

BackgroundSuccessful collective decision-making depends on groups of animals being able to make accurate choices while maintaining group cohesion. However, increasing accuracy and/or cohesion usually decreases decision speed and vice-versa. Such trade-offs are widespread in animal decision-making and result in various decision-making strategies that emphasize either speed or accuracy, depending on the context. Speed-accuracy trade-offs have been the object of many theoretical investigations, but these studies did not consider the possible effects of previous experience and/or knowledge of individuals on such trade-offs. In this study, we investigated how previous knowledge of their environment may affect emigration speed, nest choice and colony cohesion in emigrations of the house-hunting ant Temnothorax albipennis, a collective decision-making process subject to a classical speed-accuracy trade-off.Methodology/Principal FindingsColonies allowed to explore a high quality nest site for one week before they were forced to emigrate found that nest and accepted it faster than emigrating naïve colonies. This resulted in increased speed in single choice emigrations and higher colony cohesion in binary choice emigrations. Additionally, colonies allowed to explore both high and low quality nest sites for one week prior to emigration remained more cohesive, made more accurate decisions and emigrated faster than emigrating naïve colonies.Conclusions/SignificanceThese results show that colonies gather and store information about available nest sites while their nest is still intact, and later retrieve and use this information when they need to emigrate. This improves colony performance. Early gathering of information for later use is therefore an effective strategy allowing T. albipennis colonies to improve simultaneously all aspects of the decision-making process – i.e. speed, accuracy and cohesion – and partly circumvent the speed-accuracy trade-off classically observed during emigrations. These findings should be taken into account in future studies on speed-accuracy trade-offs.

Highlights

Cohesive animal groups often have to make consensual decisions to prevent the group from splitting apart and to preserve the advantages of social life, even though collective decision outcomes may sometimes be sub-optimal for certain group members [1]
We found that familiarization with a high quality and a low quality nest sites prior to emigration led to increased group cohesion and improved both speed and accuracy of emigrations, in apparent contradiction with the classical implications of a speed-accuracy trade-off
Our results show that colonies of T. albipennis gather information about the location of available good nest sites prior to emigration, while their own nest is still intact, and can later retrieve and use that information when they have to emigrate

Summary

Introduction

Cohesive animal groups often have to make consensual decisions to prevent the group from splitting apart and to preserve the advantages of social life, even though collective decision outcomes may sometimes be sub-optimal for certain group members [1]. Speed-accuracy trade-offs in collective decision-making have recently received considerable attention and many experimental and theoretical studies have attempted to describe such trade-offs, identify their underlying causes and investigate optimal strategies to achieve a suitable compromise between speed and accuracy depending on the context [2,3,4,5,6,7,8,9,10] All these studies shared the common assumption that information gathering should start simultaneously with the decision-making process, and have imposed this constraint experimentally by using naıve subjects. We investigated how previous knowledge of their environment may affect emigration speed, nest choice and colony cohesion in emigrations of the house-hunting ant Temnothorax albipennis, a collective decision-making process subject to a classical speed-accuracy trade-off

Methods

Results

Conclusion